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| United States Patent |
5,013,796
|
|
Hayashi
, et al.
|
May 7, 1991
|
Nitrile group-containing highly saturated copolymer rubber and rubber
composition having improved cold resistance
Abstract
A nitrile group-containing, highly saturated copolymer rubber is disclosed,
the copolymer chain of which is comprised of (1) 5 to 40% by weight of
units of an unsaturated nitrile monomer, (2) 1 to 80% by weight of units
of a monomer selected from a fluorine-free unsaturated carboxylic acid
ester monomer and a fluorine-containing vinyl monomer and (3) up to 20% by
weight of units of a conjugated diene monomer, with the balance being (4)
units of a hydrogenated conjugated diene monomer, wherein the sum of the
contents of the monomer units (1) and (2) is 30 to 90% and the sum of the
contents of the monomer units (3) and (4) is 10 to 70% by weight. This
copolymer rubber results in a rubber composition having an improved cold
resistance.
| Inventors:
|
Hayashi; Sachio (Tokyo, JP);
Kubo; Yoichiro (Kanagawa, JP);
Watanabe; Noboru (Kanagawa, JP);
Aimura; Yoshiaki (Kanagawa, JP)
|
| Assignee:
|
Nippon Zeon Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
575702 |
| Filed:
|
August 31, 1990 |
Foreign Application Priority Data
| Current U.S. Class: |
525/326.2; 525/338; 525/339 |
| Intern'l Class: |
C08F 008/04 |
| Field of Search: |
525/326.2,338,339
|
References Cited
U.S. Patent Documents
| 861054 | Apr., 1969 | Dickakian | 525/339.
|
| 3264272 | Aug., 1966 | Rees | 525/339.
|
| 4001193 | Jan., 1977 | van Bonin et al. | 525/379.
|
| 4404329 | Sep., 1983 | Maeda et al. | 525/329.
|
| 4525539 | Jun., 1985 | Feirung | 525/326.
|
| 4828923 | May., 1989 | Nakagawa et al. | 525/326.
|
| 4829128 | May., 1989 | Boding et al. | 525/338.
|
Primary Examiner: Libman; Bernard
Attorney, Agent or Firm: Armstrong, Nikaido, Marmelstein, Kubovcik & Murray
Parent Case Text
This is a division of application Ser. No. 543,013filed June 25, 1990,
which is a division of application Ser. No. 326,862, filed Mar. 21, 1989,
now U.S. Pat. No. 4,956,417.
Claims
We claim:
1. A nitrile group-containing, highly saturated copolymer rubber, the
copolymer chain of which comprises, based on the weight of the copolymer
chain, (1) 5 to 40% by weight of units of an unsaturated nitrile monomer,
(2) 1 to 80% by weight of units of a fluorine-containing vinyl monomer and
(3) up to 20% by weight of units of a conjugated diene monomer, with the
balance being (4) units of a hydrogenated conjugated diene monomer,
wherein the sum of the contents of the monomer units (1) and (2) is 30 to
90% by weight and the sum of the contents of the monomer units (3) and (4)
is 10 to 70% by weight.
2. The copolymer rubber according to claim 1 wherein the unsaturated
nitrile monomer is selected from the group consisting of acrylonitrile,
methacrylonitrile and .alpha.-chloroacrylonitrile.
3. The copolymer rubber according to claim 1 wherein the
fluorine-containing vinyl monomer is selected from the group consisting of
fluoroalkyl acrylates and fluoroalkyl methacrylates, having 3 to 21
fluorine atoms in the fluoroalkyl group.
4. The copolymer rubber according to claim 1 wherein the amount of the
monomer units (1) is 10 to 35% by weight, the amount of the monomer units
(2) is 5 to 60% by weight, and the sum of the amounts of the monomer units
(1) and (2) is 40 to 90% by weight.
5. The copolymer rubber according to claim 1 wherein the conjugated diene
monomer is selected from the group consisting of butadiene and isoprene.
6. The copolymer rubber according to claim 1 wherein the amount of the
monomer units (3) is up to 15% by weight and the sum of the amounts of the
monomer units (3) and (4) is 10 to 60% by weight.
7. A rubber composition comprising 25 to 90% by weight, based on the rubber
composition, of a nitrile group-containing, highly saturated copolymer
rubber and 75 to 10% by weight, based on the rubber composition, of
additives; the copolymer claim of said nitrile group-containing, highly
saturated copolymer rubber comprising, based on the weight of the
copolymer chain (1) 5 to 40% by weight of units of an unsaturated nitrile
monomer, (2) 1 to 80% by weight of units of a fluorine-containing vinyl
monomer and (3) up to 20% by weight of units of a conjugated diene
monomer, with the balance being (4) units of a hydrogenated conjugated
diene monomer, wherein the sum of the contents of the monomer units (1)
and (2) is 30 to 90% and the sum of the contents of the monomer units (3)
and (4) is 10 to 70% by weight.
8. The rubber composition according to claim 7 wherein the unsaturated
nitrile monomer is selected from the group consisting of acrylonitrile,
methacrylonitrile and .alpha.-chloroacrylonitrile.
9. The rubber composition according to claim 7 wherein the
fluorine-containing vinyl monomer is selected from the group consisting of
fluoroalkyl acrylates and fluoroalkyl methacrylates, having 3 to 21
fluorine atoms in the fluoroalkyl group.
10. The rubber composition according to claim 7 wherein the amount of the
monomer units (1) is 10 to 35% by weight, the amount of the monomer units
(2) is 5 to 60% by weight, and the sum of the amounts of the monomer units
(1) and (2) is 40 to 90% by weight.
11. The rubber composition according to claim 7 wherein the conjugated
diene monomer is selected from the group consisting of butadiene and
isoprene.
12. The rubber composition according to claim 7 wherein the amount of the
monomer units (3) is up to 15% by weight and the sum of the amounts of the
monomer units (3) and (4) is 10 to 60% by weight.
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a rubber composition having an improved
cold resistance, and comprising, as a rubber component, a nitrile
group-containing copolymer having a specific composition and a reduced
amount of an unsaturated bond.
(2) Description of the Related Art
When used for a control of automobile exhaust emissions, rubber parts
disposed in the vicinity of an engine must have a high heat resistance. To
meet this demand, a nitrile group-containing, highly saturated copolymer
rubber formed by hydrogenating a part or all of carbon-to-carbon double
bond-containing monomer units in a nitrile group-containing hydrocarbon
rubber such as an acrylonitrile/butadiene copolymer rubber (hereinafter
referred to as "NBR") was developed and is now in use (see U.S. Pat. No.
4,404,329).
This rubber has an ozone resistance and heat resistance superior to those
of conventional NBR, but has a cold resistance inferior to that of NBR in
some cases depending upon the nitrile group content or the unsaturation
degree of the main chain of the polymer.
Due to recent advances in this field, the range of temperatures of the
atmospheres in which various rubber parts are used has been extended to
lower and higher temperatures and therefore, the development of a nitrile
group-containing, highly saturated copolymer rubber composition having an
improved cold resistance is urgently required in this field.
In a conventional NBR, a reduction of the nitrile group content will
improve the cold resistance. For example, in the TR test specified in ASTM
D-1329 (an elongated test piece is frozen, the temperature is gradually
elevated, and the recovery of the elongated test piece is measured: more
specifically, the temperature at which the length of the test piece is
contracted, i.e., recovered, by 10% by elevation of the temperature is
designated as TR10), NBR having a bonded acrylonitrile content of 37% by
weight shows a TR10 value of -20.5.degree. C., but if the bonded
acrylonitrile content is reduced to 28% by weight, the TR10 value is
lowered to -31.degree. C.
Nevertheless, a nitrile group-containing, highly saturated copolymer rubber
is different from NBR in that, even if the nitrile group content is
reduced, the cold resistance is not always improved. For example, the TR10
of a rubber comprising 5% by weight of butadiene units and 37% by weight
of acrylonitrile units, with the balance being hydrogenated butadiene
units, is -24.5.degree. C. but the TR10 of a rubber comprising 5% by
weight of butadiene units and 28% by weight of acrylonitrile units, with
the balance being hydrogenated butadiene units, is -20.degree. C., and the
cold resistance is not improved even if the acrylonitrile content is
reduced.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide a
nitrile group-containing, highly saturated copolymer rubber having an
improved cold resistance, and a composition comprising this copolymer
rubber.
More specifically, in accordance with one aspect of the present invention,
there is provided a nitrile group-containing, highly saturated copolymer
rubber the copolymer chain of which comprises (1) 5 to 40% by weight of
units of an unsaturated nitrile monomer, (2) 1 to 80% by weight of units
of a monomer selected from a fluorine-free unsaturated carboxylic acid
ester and a fluorine-containing vinyl monomer, and (3) up to 20% by weight
of units of a conjugated diene monomer, with the balance being (4) units
of a hydrogenated conjugated diene monomer, wherein the sum of the
contents of the monomer units (1) and monomer units (2) is 30% to 90% by
weight and the sum of the contents of the monomer units (3) and monomer
units (4) is 10 to 70% by weight.
In accordance with another aspect of the present invention, there is
provided a rubber composition having an improved cold resistance, which
comprises a nitrile group-containing, highly saturated copolymer rubber as
set forth above, and additives.
When the rubber composition of the present invention is used, a cured
product (comprising 40 parts by weight of SRF carbon black and 100 parts
by weight of the rubber without a plasticizer) having a TR10 lower than
-26.degree. C., which is not attainable when the butadiene units of NBR
are highly hydrogenated, can be prepared.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
From the viewpoint of the oil resistance and cold resistance, in the
nitrile group-containing, highly saturated copolymer of the present
invention, the content of the nitrile group-containing monomer units (1)
is 5 to 40% by weight, preferably 10 to 35% by weight. If the content of
the monomer units (1) is lower than 5% by weight, the oil resistance is
poor, and if the content of the monomer units (1) exceeds 40% by weight,
there is little improvement of the cold resistance.
The content of the units (2) of the fluorine-free unsaturated carboxylic
acid ester monomer and or the fluorine-containing vinyl monomer is 1 to
80% by weight preferably 15 to 60% by weight. If the content of the
monomer units (2) is lower than 1% by weight, there is little improvement
of the cold resistance and if the content of the monomer units (2) exceeds
80% by weight, the cold resistance is improved but the oil resistance
becomes poor.
From the viewpoint of the heat resistance, the content of the conjugated
diene monomer units (3) in the copolymer rubber is up to 20% by weight,
preferably up to 15% by weight. The content other than the content of the
monomer units (1), (2) and (3) is composed of the hydrogenated conjugated
diene monomer units (4).
Moreover, to maintain a good balance between the oil resistance and cold
resistance, the sum of the contents of the monomer units (1) and (2) is 30
to 90% by weight, preferably 40 to 90% by weight. Surprisingly, the cold
resistance is not improved outside this range. Furthermore, to maintain a
good balance between the heat resistance and cold resistance, the sum of
the contents of the monomer units (3) and (4) is 10 to 70% by weight,
preferably 10 to 60% by weight.
The content of the monomer units (2), the sum of the contents of the
monomer units (1) and (2) and the sum of the contents of the monomer units
(3) and (4), which are desired for the improvement of the cold resistance,
vary depending upon the particular fluorine-free unsaturated carboxylic
acid ester monomer and/or the particular fluorine-containing vinyl
monomer. More specifically, where a fluorine-free unsaturated carboxylic
acid ester is used as the monomer for forming the monomer units(2), it is
preferable that the content of the monomer units (2) is 15 to 60% by
weight, the sum of the contents of the monomer units (1) and (2) is 40 to
90% by weight, more preferably 55 to 90% by weight, and the sum of the
contents of the monomer units (3) and (4) is 10 to 60% by weight, more
preferably 10 to 45 by weight. Where a fluorine-containing vinyl monomer
is used as the monomer for forming the monomer units (2), it is preferable
that the content of the monomer units (2) is 5 to 60% by weight, the sum
of the contents of the monomer units (1) and (2) is 40 to 90% by weight,
and the sum of the contents of the monomer units (3) and (4) is 10 to 60%
by weight.
The nitrile group-containing, highly saturated copolymer rubber of the
present invention is obtained by hydrogenating conjugated monomer units in
a copolymer rubber, formed by copolymerizing (1) an unsaturated nitrile
monomer, (2) at least one monomer selected from fluorine-free unsaturated
carboxylic acid esters and fluorine-containing vinyl monomers, and (3) a
conjugated diene monomer by a conventional method.
The monomers to be used for the production of the copolymer rubber of the
present invention will now be described.
As the unsaturated nitrile monomer, there can be mentioned, for example,
acrylonitrile, methacrylonitrile and .alpha.-chloroacrylonitrile.
As the fluorine-free unsaturated carboxylic acid ester monomer, there can
be mentioned, for example, alkyl acrylates and methacrylates having 1 to
18 carbon atoms in the alkyl group, such as methyl acrylate, ethyl
acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl
acrylate, n-hexyl acrylate, 2-methylpentyl acrylate, n-octyl acrylate,
2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate and ethyl
methacrylate; alkoxyalkyl acrylates having 2 to 12 carbon atoms in the
alkoxyalkyl group, such as methoxymethyl acrylate, methoxyethyl acrylate,
ethoxyethyl acrylate, butoxyethyl acrylate, ethoxy-propyl acrylate,
methoxyethoxy acrylate and ethoxybutoxy acrylate; cyanoalkyl acrylates
having 2 to about 12 carbon atoms in the cyanoalkyl group, such as
.alpha.- and .beta.-cyanoethyl acrylates, .alpha.-, .beta.- and
.gamma.-cyanopropyl acrylates, cyanobutyl acrylate, cyanohexyl acrylate
and cyano-octyl acrylate; hydroxyalkyl acrylates having 1 to 18 carbon
atoms in the hydroxyalkyl group such as 2-hydroxyethyl acrylate and
hydroxypropyl acrylate; aminoalkyl esters of ethylenically unsaturated
carboxylic acids, having 1 to 12 carbon atoms in the aminoalkyl group,
such as methylaminoethyl acrylate, t-butylaminoethyl acrylate,
dimethylaminoethyl acrylate, dimethylaminopropyl acrylate,
diethylaminoethyl acrylate, dibutylaminoethyl acrylate, methylaminoethyl
methacrylate, t-butylaminoethyl methacrylate, dimethylaminoethyl
methacrylate, dimethylaminopropyl acrylate, diethylaminoethyl methacrylate
and dibutylaminoethyl methacrylate; and mono- and di-alkyl esters of
unsaturated carboxylic acids, having 1 to 8 carbon atoms in the alkyl
group, such as monoethyl maleate, dimethyl maleate, dimethyl fumarate,
diethyl fumarate, di-n-butyl fumarate, di-2-ethylhexyl fumarate, dimethyl
itaconate, and di-n-butyl itaconate.
Of these fluorine-free unsaturated carboxylic acid ester monomers, alkyl
acrylates and methacrylates having 4 to 12 carbon atoms in the alkyl
group, aminoalkyl acrylates and methacrylates having 1 to 12 carbon atoms
in the aminoalkyl group, and hydroxyalkyl acrylates having 1 to 18 carbon
atoms in the hydroxyalkyl group are preferable.
As the fluorine-containing vinyl monomer, there can be mentioned, for
example, fluoroalkyl acrylates and methacrylates having 3 to 21 fluorine
atoms in the fluoroalkyl group, such as trifluoroethyl acrylate,
tetrafluoropropyl acrylate, pentafluoropropyl acrylate, heptafluorobutyl
acrylate, octafluoropentyl acrylate, nonafluoropentyl acrylate,
undecafluorohexyl acrylate, pentadecafluoro-octyl acrylate,
heptadecafluorononyl acrylate, heptadecafluorodecyl acrylate,
nonadecafluorodecyl acrylate, trifluoroethyl methacrylate,
tetrafluoropropyl methacrylate, octafluoropentyl methacrylate,
dodecafluoroheptyl methacrylate, pentadecafluoro-octyl acrylate, and
hexadecafluorononyl methacrylate; fluorine-substituted benzyl acrylates
and methacrylates such as fluorobenzyl acrylate, difluorobenzyl acrylate,
fluorobenzyl methacrylate and difluorobenzyl methacrylate; fluoroalkyl
vinyl ethers having 1 to 8 carbon atoms in the fluoroalkyl group, such as
fluoroethyl vinyl ether, fluoropropyl vinyl ether, trifluoromethyl vinyl
ether, trifluoroethyl vinyl ether, perfluoropropyl vinyl ether and
perfluorohexyl vinyl ether; and o- and p-trifluoromethylstyrenes, vinyl
pentafluorobenzoate, difluoroethylene and tetrafluoroethylene. Of these
fluorine-containing vinyl monomers fluoroalkyl acrylates and methacrylates
having 3 to 21 fluorine atoms in the fluoroalkyl group are preferable.
As the conjugated diene monomer, there can be mentioned, for example,
1,3-butadiene, 2,3-dimethylbutadiene, isoprene and 1,3-pentadiene.
Parts of the above-mentioned monomers can be substituted by monomers
copolymerizable with the above-mentioned monomers, for example, vinyl
monomers such as styrene and vinylpyridine and non-conjugated diene
monomers such as vinylnorbornene, dicyclopentadiene and 1,4-hexadiene, so
long as the intended object of the present invention can be attained.
The nitrile group-containing, highly saturated copolymer rubber of the
present invention is obtained by copolymerizing the above-mentioned
monomers by customary polymerization procedures, and then hydrogenating
the conjugated diene monomer units of the thus obtained copolymer rubber.
For example, there can be mentioned copolymer rubbers obtained by
hydrogenating the butadiene units and isoprene units of copolymer rubbers
such as a butadiene/butyl acrylate/acrylonitrile copolymer rubber, a
butadiene/isoprene/butyl acrylate/acrylonitrile copolymer rubber, a
butadiene/2-ethylhexyl acrylate/acrylonitrile copolymer rubber, a
butadiene/trifluoroethyl acrylate/acrylonitrile copolymer rubber, a
butadiene/trifluoroethyl methacrylate/acrylonitrile copolymer rubber, a
butadiene/diethylaminoethyl methacrylate/acrylonitrile copolymer rubber
and a butadiene/di-n-butyl itaconate/acrylonitrile copolymer rubber.
A rubber composition of the present invention is prepared by mixing the
nitrile group-containing, highly saturated copolymer rubber with various
additives customarily used in the rubber industry in a conventional mixer.
The kinds and amounts incorporated of the additives are determined in
accordance with the intended object (use) of the rubber composition.
Usually, the rubber composition comprises, based on the weight of the
rubber composition, 25 to 90% by weight of the nitrile group-containing,
highly saturated copolymer rubber of claim and 75 to 10% by weight of
additives.
As the additives, there can be mentioned sulfur-curing systems comprising a
sulfur donor compound such as sulfur or tetramethylthiuram disulfide, zinc
oxide, stearic acid and a curing promoter of the guanidine, thiazole,
thiuram or dithiosulfate type; organic peroxide-curing systems comprising
an organic peroxide such as dicumyl peroxide or
2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3 and a cross-linking agent such
as triallyl cyanurate or trimethylolpropane trimethacrylate; carbon blacks
of various grades such as SRF, HAF and FEA, reinforcers such as silica,
talc and calcium carbonate, fillers, plasticizers, process oils,
processing assistants, and aging-preventing agents.
By using the rubber composition of the present invention, a cured product
having a TR10 lower than -26.degree. C., which is not attainable by a
composition comprising a conventional highly saturated NBR, can be
prepared (40 parts by weight of SRF carbon black and 100 parts by weight
of the rubber; a plasticizer is not incorporated).
The rubber composition of the present invention has the characteristics of
the nitrile group-containing, highly saturated copolymer rubber, such as a
high ozone resistance, high heat resistance, and high oil resistance, and
further, the rubber composition has an excellent cold resistance.
Accordingly, the rubber composition of the present invention is effective
for use in the production of rubber products which are in contact with an
oil or gas during use, and for which a high heat resistance and oil
resistance are required, especially rubber products for which a high cold
resistance is required.
The rubber composition of the present invention can be widely used in the
production of, for example, sealing rubber products such as an O-ring, a
packing or a gasket used for a bearing of a rotating device; belts such as
a conveyor belt, a V-belt or a timing belt; valves and valve-sealing
materials; oil well packers, well-head sealing materials, BOP (blow-out
preventers) and bladders; cushioning materials and vibration insulators;
ship and automobile bearing seals such as crank shaft seals, bearing
seals, rotary seals of accelerators and stern tube seals; various
diaphragms; and hoses such as automobile fuel hoses, marine hoses, riser
hoses and flow line hoses, and further, can be used in the energy field,
for example, as articles for geothermal electric power generation.
The present invention will now be described in detail with reference to the
following examples. Note, in the examples, comparative examples and
referential examples, all of "parts" and "%" are by weight unless
otherwise indicated.
EXAMPLES 1 THROUGH 10 AND COMPARATIVE EXAMPLES 1 THROUGH 10
An acrylonitrile/butadiene copolymer rubber or
acrylonitrile/butadiene/fluorine-free unsaturated carboxylic acid ester
monomer terpolymer rubber, prepared by a customary emulsion
polymerization, was dissolved in methyl isobutyl ketone, and the butadiene
units of the rubber were partially hydrogenated in a pressure-resistant
vessel by using a Pd/silica catalyst, to obtain a highly saturated
copolymer rubber. The contents of the monomer units in the rubber are
shown in Table 1.
The obtained highly saturated copolymer rubber was then mixed with
additives shown in Table 2 on a cooling roll, to obtain a rubber
composition, and the rubber composition was heated under pressure at
170.degree. C. for 15 minutes to obtain a cured product. The TR test of
the cured product was carried out according to ASTM D-1329, and the other
physical properties of the cured product were measured according to JIS
(Japanese Industrial Standard) K-6301. The results are shown in Table 1.
TABLE 1
__________________________________________________________________________
Examples of the Invention
2 3 4 5 6 7 8 9 10
__________________________________________________________________________
Monomer units (%):
Acrylonitrile 15 14 14 15 15 20 20 20 20 20
Diethyl itaconate
42 -- -- -- -- 37 -- -- -- --
Di-n-butyl itaconate
-- 45 -- -- -- -- 38 -- -- --
Diethylaminoethyl methacrylate
-- -- 45 -- -- -- -- 39 -- --
Butyl acrylate -- -- -- 43 -- -- -- -- 35 --
2-Ethylhexyl acrylate
-- -- -- -- 45 -- -- -- -- 38
Butadiene 5 5 13 7 5 5 5 6 10 8
Hydrogenated butadiene
38 36 28 35 35 38 37 35 35 34
Physical properties in normal
state:
Tensile strength (kg/cm.sup.2)
186
190
182
210
213
214
203
190
210
224
Elongation (%) 230
250
530
250
240
370
240
380
230
270
Hardness (points)
61 58 57 61 62 61 61 57 60 64
Change in physical properties
after heat aging at 150.degree. C. for
72 hours:
Change ratio of tensile
-5 -12
-34
-18
-11
-1 -20
-24
-16
-15
strength (%)
Change of elongation (%)
-15
-12
-30
-20
-25
-12
-21
-23
-22
-19
Change of hardness
-4 -2 -2 -1 -2 -3 -1 -1 -1 -1
TR-10 (.degree.C.)
-35
-39
-41
-30
-26
-33
-35
-38
-27
-26
__________________________________________________________________________
Comparative Examples
1 2 3 6 7 8 9 10
__________________________________________________________________________
Monomer units (%):
Acrylonitrile 15 14 14 20 20 45 20 34
Diethyl itaconate 10 -- -- -- -- 10 -- --
Di-n-butyl itaconate -- 10 -- 5 -- -- -- --
Diethylaminoethyl methacrylate
-- -- 10 -- 5 -- -- --
Butyl acrylate -- -- -- -- -- -- -- --
2-Ethylhexyl acrylate -- -- -- -- -- -- -- --
Butadiene 5 5 13 10 10 5 5 5
Hydrogenated butadiene
70 71 63 65 65 40 75 61
Physical properties in normal
state:
Tensile strength (kg/cm.sup.2)
210
200
200
220
210
230
190
265
Elongation (%) 270
280
380
290
350
300
300
430
Hardness (points) 61 59 63 60 62 62 65 65
Change in physical properties
after heat aging at 150.degree. C. for
72 hours:
Change ratio of tensile
-7 -15
-35
-12
-32
-10
-8 -6
strength (%)
Change of elongation (%)
-20
-20
-19
-17
-26
-15
-10
-7
Change of hardness +1 +2 +3 +1 +2 +1 +2 +5
TR-10 (.degree.C.) -18
-22
-15
-15
-17
-17
-10
-24
__________________________________________________________________________
TABLE 2
______________________________________
(Recipe)
______________________________________
Highly saturated copolymer rubber
100 parts
Zinc oxide 5 parts
Stearic acid 1 part
SRF carbon black 40 parts
Peroximon F40.sup.1 5 parts
______________________________________
Note
.sup.1 m,p-di-isopropylbenzene .alpha.,.alpha.',bis-t-butyl peroxide
supplied by Montecatini (Italy)
As apparent from Comparative Examples 1.through 8 in Table 1, the cold
resistance (TR10) of a copolymer rubber containing unsaturated carboxylic
acid ester units which fails to satisfy the requirements of the present
invention, is not improved.
EXAMPLES 11 THROUGH 21 AND COMPARATIVE EXAMPLES 11 THROUGH 14
A rubber composition was prepared according to a recipe shown in Table 2 by
using a highly saturated copolymer rubber shown in Table 3, which was
prepared in the same manner as described in Example 1, and the rubber
composition was heated under pressure at 170.degree. C. for 15 minutes to
obtain a cured product having the properties shown in Table 3.
TABLE 3
__________________________________________________________________________
Comparative
Examples of the Invention Examples
11 12 13 14 15 16 17 18 19 20 21 11 12 13 14
__________________________________________________________________________
Monomer units (%):
Acrylonitrile 23 28 34 22 28 23 34 25 32 24 31 21 25 24 25
Trifluoroethyl acrylate
20 15 10 32 23 -- -- -- -- -- -- 5 -- -- --
Trifluoroethyl methacrylate
-- -- -- -- -- 22 10 -- -- -- -- -- -- -- --
Tetrafluoropropyl acrylate
-- -- -- -- -- -- -- 30 19 -- -- -- 3 -- --
Octafluoropentyl acrylate
-- -- -- -- -- -- -- -- -- 30 20 -- -- 3 --
Butadiene 10 10 10 5 5 5 10 5 5 5 5 5 5 5 5
Hydrogenated butadiene
47 47 46 41 44 50 46 40 44 41 44 69 67 68 70
Physical properties in normal
state:
Tensile strength (kg/cm.sup.2)
223
210
238
243
263
206 246
224
254
210
245
200 230
240
270
Elongation (%) 290
260
260
220
300
280 320
240
280
220
280
290 290
300
260
Hardness (points)
66 65 65 65 66 64 64 71 70 70 70 64 63 65 64
Change in physical properties
after heat aging at 150.degree. C. for
72 hours:
Change ratio of tensile
-26
-32
-12
-14
-8 -31 -6 -9 -8 .+-.0
-8 -10 -16
-20
-20
strength (%)
Change of elongation (%)
-23
-25
-20
-14
-13
-29 -22
-12
-21
-14
-21
-13 -24
-20
-22
Change of hardness
+2 +1 +2 +2 + 2
+2 +2 +1 +3 +2 +3 +3 +5 +4 +6
TR-10 (.degree.C.)
-28
-29
-30
-30
-30
-28 -26
-30
-29
-30
-29
-15 -19
-18
-14
__________________________________________________________________________
EXAMPLE 22 AND COMPARATIVE EXAMPLE 15
Highly saturated copolymer rubbers having the monomer units shown in Table
4 were prepared in the same manner as described in Example 1 by using a
butadiene/isoprene/butyl acrylate/acrylonitrile copolymer (composition
ratio=52/10/10/28) and a butadiene/isoprene/acrylonitrile copolymer rubber
composition ratio=62/10/28) for comparison.
Rubber compositions were obtained by mixing the copolymer rubbers with
additives shown in Table 5 on a roll, the rubber compositions were heated
under pressure at 160.degree. C. for 20 minutes to obtain cured products,
and the characteristic properties thereof were measured. The results are
shown in Table 4.
TABLE 4
______________________________________
Comparative
Example
Example
22 15
______________________________________
Monomer units (%):
Acrylonitrile 28 28
Butyl acrylate 10 --
Diene 11 11
Hydrogenated diene 51 61
Physical properties in normal
state:
Tensile strength (kg/cm.sup.2)
239 252
Elongation (%) 240 300
Hardness (points) 64 63
Change in physical properties
after heat aging at 150.degree. C. for
72 hours:
Change ratio of tensile
-16 -17
strength (%)
Change of elongation (%)
-28 -29
Change of hardness (points)
+4 +5
TR-10 (.degree.C.) -30 -21.5
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TABLE 5
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(Recipe)
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Highly saturated copolymer rubber
100 parts
Zinc oxide 5 parts
Stearic acid 1 part
Sulfur 0.5 part
SRF carbon black 40 parts
Tetramethylthiuram disulfide
2 parts
2-Mercaptobenzothiazole 0.5 part
______________________________________
EXAMPLE 23
Each of the hydrogenated to polymer rubbers of the present invention
obtained in Example 1 through 21 was mixed with the additives shown in
Table 5. The obtained rubber compositions were heated under pressure at
160.degree. C. for 20 hours, and the TR10 of each of the obtained cured
products was measured. The results were substantially the same as the
results obtained in Examples 1 through 21.
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